EP3779611A1 - Electromechanical watch - Google Patents

Abstract

The electromechanical watch (2) of the invention comprises an electromechanical motor (4) mechanically coupled to an analog display (AD) and formed by two coils (B1, B2) through which the magnetic circuit (10) of the stator passes. A first of the two coils is connected to a voltage detection circuit (CD1, CD2) arranged to be able to detect a possible induced voltage in this first coil during intervening time intervals, in a step-by-step mode of operation of the motor. , between driving pulses and in particular detecting whether an unwanted step is taken by the rotor (18) during these time intervals. The electromechanical watch comprises at least one switch (T1, T2, T3) which is controlled by an electronic control circuit (CEC) so as to short-circuit the second coil during each of said time intervals, thereby to passively retain the rotor in the rest position in which it is momentarily between the driving impulses.

Description

Technical area

The present invention relates to electromechanical watches which include an analog display and which, in the event of shocks, are liable to suffer unwanted movements of this analog display. In particular, the present invention relates to a system making it possible to make such electromechanical watches more robust in the event of impacts while making it possible to detect unwanted steps, that is to say steps not commanded.

Technological background

The problem of the risk of unwanted steps in the event of shocks for electromechanical watches has been known for a long time and various solutions have been provided to this problem.

The document EP 1 693 720 proposes a system in which it is provided to detect an impact undergone by an electromechanical watch by means of an impact detection unit which is connected to the ends of the single coil of the stepping motor during the time intervals between the driving impulses supplied to the motor. Indeed, when a needle moves during an impact, the movement of the permanent magnet rotor which results therefrom generates an electrical signal in the coil that the impact detection unit can detect. Following the detection of an untimely movement of the rotor via the electrical signal generated in the coil, it is planned to send an electrical impulse to block the rotor so as to prevent the stepping motor from taking one or more steps. untimely. This solution has several drawbacks. First, connecting the coil to a circuit for detecting an electrical signal induced in the coil by movement of the rotor requires maintaining a very high impedance for the coil, in which therefore no current can flow. Thus, this solution does not make it possible to benefit from a damping of an untimely movement of the rotor by virtue of a current induced by such a movement during the time intervals intervening between the drive pulses. In this state, the electromechanical motor is therefore vulnerable to shocks or other sudden accelerations that the watch may undergo, even if it can then detect such events when they generate unwanted movements of the analog display and therefore of the rotor which is mechanically connected to this analog display. Second, the system provides for detecting whether the watch is impacted and then reacting to this information by generating a rotor locking pulse. Thus, it is possible that the reaction is too late and / or insufficient to prevent the motor from taking at least one unwanted step. In addition, if the blocking pulse fails to prevent an unwanted step, then this blocking pulse in turn generates an unwanted second step. Finally, the generation of blocking pulses can consume a lot of electrical energy. If the detection threshold is provided relatively low to ensure rapid detection and a reaction in the best time, blocking pulses are often generated so that the autonomy of the electromechanical watch is reduced.

The document EP 3 171 231 also describes a system of the type proposed in the document cited above. A shock detection circuit is provided here which is connected to at least one electrical terminal of the electromechanical motor so as to be able to detect a voltage induced in the single coil of the stepping motor in the event of shocks suffered by the watch which cause an untimely displacement of the analog display, that is to say of at least one indicator in kinematic link with the stepping motor. Provision is also made here to generate a blocking pulse following the detection of a shock. This embodiment raises the same problems as those described in connection with the document cited above. It will also be noted that a circuit shock detection device can also be arranged to detect whether a desired step has not taken place, so as to be able to then generate a catching step.

It will be noted that a device has been proposed which makes it possible to count unwanted steps of the stepping motor as well as the direction of rotation of the rotor during such untimely steps. Following a shock having generated one or more unwanted steps of the rotor, it is possible to correct the error generated in the analog display in an appropriate manner, either by correction steps, or, when the direction of unwanted steps is that provided for driving the analog display, by inhibiting a number of drive pulses corresponding to the number of unwanted steps via the motor control which periodically generates drive pulses to drive the analog display. With such a solution, it is no longer necessary to electrically block the rotor by an electrical signal when a shock is detected and therefore to ensure a sufficiently rapid and strong reaction of the electronic circuit of the watch. This solution has the advantage of not limiting the unbalance that an indicator forming the analog display may present. However, these means of counting unwanted steps via the detection of an electrical signal induced in the motor coil prevents the step-by-step motor from being able passively, in a “natural” manner, to oppose such unwanted steps by shock cases; which increases the power consumption of the electromechanical watch.

The patent application CH 0026002 discloses a single-phase stepper motor provided with two coils. According to the teaching of this document, the two coils are arranged in series to generate strong pulses allowing the rotor to rotate in a first direction, known as the preferred direction, and in parallel to generate pulses allowing the rotor to then rotate in the direction reverse in the preferential sense. Between the pulses used to drive the rotor in one direction or the other, provision is made to short-circuit the two coils to brake the rotor and thus limit a number of unwanted steps in the event of an impact. No shock or shock detection circuit unwanted steps and no correction circuit for such unwanted steps is provided. Depending on the situation and the intended training mode, one unwanted step and 'naturally followed' by a corrective step or two other steps in the wrong direction, thus being able to leave a three step error following a shock.

Summary of the invention

The aim of the present invention is to remedy the aforementioned technical problems.

To this end, the invention relates to an electromechanical watch, the electromechanical motor of which is formed by a stator, comprising a magnetic circuit and a first coil traversed by this magnetic circuit, and by a rotor provided with a permanent magnet coupled to the magnetic circuit, this magnetic circuit defining at least one minimum energy position for the rotor which is mechanically coupled to the analog display of the watch. The first coil is arranged so as to be able, in a step-by-step mode of operation of the electromechanical motor, to be connected to a voltage detection circuit which is arranged to detect any induced voltage in this first coil during intervals of time between the drive pulses supplied to the motor and in particular to detect whether an uncontrolled step is taken by the rotor during these time intervals. Then, the electromechanical motor comprises a second coil traversed by the magnetic circuit. In addition, the electromechanical watch comprises at least one switch which is controlled by the electronic control circuit, in the step-by-step mode of operation of the electromechanical motor, so as to connect the first coil to the voltage detection circuit during of time intervals among said time intervals and shorting the second coil during at least the major part of each of these time intervals.

In a first main variant, the electromechanical watch is arranged so that the first coil is connected to the voltage detection circuit during all of said time intervals, and so that the second coil is short-circuited during at least the major part of each of said time intervals.

In a second main variant, the detection circuit and a set of switches are arranged so that each of the first and second coils can be connected to at least part of the voltage detection circuit. Then, the set of switches which is arranged and controlled by the electronic control circuit so that, during each of said time intervals, any one of the first and second coils is connected to the voltage detection circuit and the other of these first and second coils is short-circuited during at least the major part of this time interval.

Thanks to the characteristics of the electromechanical watch according to the invention, detection of any untimely steps of the rotor during an impact is preserved via at least one of the first and second coils connected to the voltage detection circuit, and in addition it is passively blocked. the rotor via the other of these two coils which is short-circuited apart from the driving pulses. Thus, the number of possible untimely steps is greatly reduced in the event of an impact and, if such an untimely step should nevertheless take place during an impact, its detection remains assured; This makes it possible, on the one hand, to subsequently correct the error generated for the analog display and, on the other hand, to possibly further increase the resistance of the motor to shock by generating a blocking pulse via one of the two coils .

Brief description of the figures

• La Figure 1 représente schématiquement un mode de réalisation d'une montre électromécanique selon l'invention, et
• La Figure 2 est un tableau donnant divers états d'un circuit de trois interrupteurs et les configurations résultantes pour les deux bobines formant le stator du moteur électromécanique de la montre de la Figure 1.

The invention will be described below in more detail with the aid of the appended drawings, given by way of non-limiting examples, in which:

• The Figure 1 schematically represents an embodiment of an electromechanical watch according to the invention, and
• The Figure 2 is a table giving various states of a circuit of three switches and the resulting configurations for the two coils forming the stator of the electromechanical motor of the watch of the Figure 1 .

Detailed description of the invention

With reference to Figures 1 and 2 , an embodiment of an electromechanical watch 2 according to the invention will be described below.

• un affichage analogique AD comprenant notamment une aiguille des heures 6 et une aiguille des minutes 8,
• un moteur électromécanique 4 formé d'un stator, comprenant un circuit magnétique 10 et une bobine B1 traversée par un noyau 14 formant le circuit magnétique, et d'un rotor 18 muni d'un aimant permanent 20 couplé magnétiquement au circuit magnétique, ce rotor étant couplé mécaniquement à l'affichage analogique,
• un circuit d'alimentation, représenté en deux parties CA1 et CA2, pour alimenter le moteur électromécanique, les deux parties du circuit d'alimentation étant reliées respectivement à une première borne électrique M1 et une deuxième borne électrique M2 du moteur électromécanique,
• un circuit électronique de commande du moteur électromécanique, ce circuit électronique de commande CEC étant agencé de manière que, dans un mode de fonctionnement pas-à-pas du moteur électromécanique, le circuit d'alimentation engendre sur commande des impulsions motrices présentant entre elles des intervalles de temps non nuls, et
• un circuit de détection de tension présentant, dans la variante représentée, deux parties CD1 et CD2 reliées respectivement aux première et deuxième bornes électriques M1 et M2, ce circuit de détection étant agencé pour pouvoir détecter une tension induite dans la bobine B1 durant lesdits intervalles de temps et notamment détecter, sur la base de cette tension induite, si un pas intempestif est effectué par le rotor 18 au cours de ces intervalles de temps.

The electromechanical watch 2 includes:

• an analog display AD comprising in particular an hour hand 6 and a minute hand 8,
• an electromechanical motor 4 formed of a stator, comprising a magnetic circuit 10 and a coil B1 traversed by a core 14 forming the magnetic circuit, and a rotor 18 provided with a permanent magnet 20 magnetically coupled to the magnetic circuit, this rotor being mechanically coupled to the analog display,
• a supply circuit, shown in two parts CA1 and CA2, for supplying the electromechanical motor, the two parts of the supply circuit being respectively connected to a first electrical terminal M1 and a second electrical terminal M2 of the electromechanical motor,
• an electronic control circuit of the electromechanical motor, this electronic control circuit CEC being arranged so that, in a step-by-step mode of operation of the electromechanical motor, the supply circuit generates on command driving pulses having between them non-zero time intervals, and
• a voltage detection circuit having, in the variant shown, two parts CD1 and CD2 connected respectively to the first and second electrical terminals M1 and M2, this detection circuit being arranged to be able to detect a voltage induced in the coil B1 during said time intervals and in particular detecting, on the basis of this induced voltage, whether an untimely step is taken by the rotor 18 during these time intervals.

The electromechanical motor 4 is of the step-by-step type, the magnetic circuit 10 defining for the rotor 18 at least one minimum energy position towards which the rotor, when it is in motion, turns in the absence of power supply. electrical and in which it remains in the absence of an electrical supply, that is to say in the absence of driving pulses supplied on command by the supply circuit. Each minimum energy position defines a stable position for the rotor in the absence of electrical power, also called 'rest position'. Thus, it is possible to detect, via the voltage induced in the coil B1, during the time intervals between the driving pulses whether the rotor is turning from a rest position in which it is momentarily.

Several documents of the prior art, in particular those cited in the technological background, describe various embodiments for the circuit for detecting an electrical signal induced in a coil of the stepping motor of an electromechanical watch and for processing the detected induced electrical signal with a view to determining whether at least one unwanted, that is to say uncontrolled, step has taken place between two drive pulses intended to operate the stepping motor. These documents of the prior art also describe, as indicated previously, various possible reactions to prevent an untimely step from being performed as soon as an uncontrolled rotation is detected and / or to count unwanted steps and the corresponding direction of rotation of so as to then correct the resulting error for the analog display. These various embodiments and possible reactions can be implemented in the circuits CA1 & CA2 for detecting a voltage induced in a coil and in the electronic control circuit CEC. It will be noted that, in a variant, only one of the two electrical terminals M1, M2 is connected to the circuit for detecting an induced voltage, which then comprises a single part CD1 or CD2.

According to the invention, the stator of the electromechanical motor further comprises a coil B2 traversed by the magnetic circuit 10, in particular by the core 14 as shown in Figure 1 . Then, in general, the electromechanical watch 2 comprises at least one switch which is controlled by the electronic control circuit CEC so as to short-circuit the coil B2 during at least the major part of each of said time intervals in the mode of. step-by-step operation of the electromechanical motor 4. It will be noted that, in another configuration of the electromechanical motor, the coil B2 can be traversed by a second core of the magnetic circuit. As the rotor permanent magnet is magnetically coupled to the magnetic circuit, this permanent magnet is magnetically coupled to the two coils B1 & B2 by the two respective cores.

In the preferred embodiment described with reference to the figures, the electromechanical watch comprises a plurality of switches T1, T2 and T3 which are arranged and controlled by the electronic control circuit CEC so that the coil B1 and the coil B2 can be arranged during the driving pulses either in series or in parallel. In addition, during said time intervals between the driving pulses, it is possible to either short-circuit the coil B2 and detect the voltage in the coil B1, or to short-circuit the coil B1 and detect the voltage in the coil B2. The table given to the Figure 2 supplies for various useful states of the three switches T1, T2 and T3, controlled respectively by three digital signals S1, S2 and S3 generated by the electronic control circuit CEC, the corresponding configurations of the coils B1 and B2. Thus, the coil connected during said time intervals to the voltage detection circuit is either coil B1 or coil B2, and the coil short-circuited during these time intervals is respectively either coil B2 or coil B1 . A closed switch (noted 'F') is conducting while an open switch (noted 'O') is not conducting.

In an above-mentioned variant, only one of the two coils can be connected to a detection circuit CD, formed by one or the other of the two parts CD1 and CD2 of such a detection circuit shown in FIG. Figure 1 . In this variant, during at least the major part of the time intervals between the driving pulses, the coil which can be connected to a detection circuit CD is connected to this coil and the other coil is short-circuited to brake any movement. of the rotor during at least the major part of said time intervals, and thus avoid unwanted steps or limit their number.

The configuration of the coils B1 and B2 in series is preferably used when applying the driving pulses to the electromechanical motor in a normal stepping mode of operation, this series configuration making it possible to minimize the electrical energy consumed. The configuration of the coils B1 and B2 in parallel is preferably used when applying driving pulses to the electromechanical motor in an accelerated mode of operation, that is to say at relatively high speed, in particular when switching on. time or an AD analog display correction operation. It will be noted that provision can also be made, if desired, to supply only one of the two coils during certain drive pulses supplied to the electromechanical motor.

Claims (4)

Electromechanical watch (2) comprising: - an analog display (AD), - an electromechanical motor (4) formed of a stator, comprising a magnetic circuit (10) and a coil (B1) through which this magnetic circuit passes, and a rotor (18) provided with a permanent magnet (20) coupled to the magnetic circuit, this magnetic circuit defining at least one position of minimum energy for the rotor, this rotor being mechanically coupled to the analog display, - a supply circuit (CA1, CA2) for supplying the electromechanical motor, this supply circuit being connected to a first electrical terminal (M1) and a second electrical terminal (M2) of this electromechanical motor, an electronic control circuit of the electromechanical motor, this electronic control circuit (CEC) being arranged so that, in a step-by-step mode of operation of the electromechanical motor, the supply circuit generates, on command, driving pulses having between them non-zero time intervals, and - a voltage detection circuit (CD1, CD2) arranged to be able to detect a voltage induced in said coil (B1) during said time intervals and in particular to detect, on the basis of this induced voltage, whether a step is taken by the rotor (18) during these time intervals; characterized in that said coil is a first coil (B1) and the stator of the electromechanical motor further comprises a second coil (B2) traversed by said magnetic circuit (10); and in that the electromechanical watch comprises at least one switch (T1, T2, T3) which is controlled by the electronic control circuit (CEC), in the step-by-step operating mode of the electromechanical motor, so as to connect the first coil to said voltage sensing circuit during intervals among said time intervals and shorting the second coil during at least the major part of each of these time intervals. Electromechanical watch (2) according to claim 1, characterized in that it is arranged so that the first coil is connected to said voltage detection circuit during all of said time intervals, and so that the second coil is short. -circuitée during at least the major part of each of said time intervals. Electromechanical watch (2) according to claim 1, characterized in that the detection circuit and a set of switches (T2, T3) are arranged so that each of the first and second coils can be connected to at least one part (CD1 , CD2) of the voltage detection circuit; and in that the set of switches is arranged and controlled by the electronic control circuit (CEC) such that during each of said time intervals any one of the first and second coils is connected to said control circuit. voltage detection and the other of these first and second coils is short-circuited during at least the major part of this time interval. Electromechanical watch according to any one of the preceding claims, characterized in that it comprises a plurality of switches (T1, T2, T3) arranged and controlled by the electronic control circuit (CEC) so that the first and second coils (B1 & B2) can be arranged either in series or in parallel during the driving pulses.

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